A TV-modulator and power supply by Amstrad for the classic CPC-computers.
If you bought an Amstrad CPC together with one of the Amstrad GT64/GT65 Green Monitors however, you might have wanted the ability to play games on the colour TV-set later, so Amstrad also made the MP-1/MP-2 devices. They provided the power needed by the CPCs, so that you didn't have to carry the monitor around just to have power, and a TV-modulator which modulated the monitor signal in a way that it could be seen on a regular TV-set.
The difference between the MP-1 and MP-2 models is just the additional 12V power supply for the CPC664/CPC6128's disk drive in the later model.
Source: CPCwiki.